/*********************************************************************
 * Copyright (C) 2001 Andrew Khan
 * <p>
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * <p>
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * <p>
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 ***************************************************************************/

package jxl.write.biff;

import jxl.CellType;
import jxl.DateCell;
import jxl.biff.DoubleHelper;
import jxl.biff.Type;
import jxl.common.Logger;
import jxl.format.CellFormat;
import jxl.write.DateFormats;
import jxl.write.WritableCellFormat;

import java.text.DateFormat;
import java.util.Calendar;
import java.util.Date;

/**
 * A date stored in the database
 */
public abstract class DateRecord extends CellValue {
    /**
     * The logger
     */
    private static Logger logger = Logger.getLogger(DateRecord.class);

    /**
     * The excel value of the date
     */
    private double value;
    /**
     * The java representation of the date
     */
    private Date date;

    /**
     * Indicates whether this is a full date, or just a time only
     */
    private boolean time;

    // The number of days between 01 Jan 1900 and 01 Jan 1970 - this gives
    // the UTC offset
    /**
     */
    private final static int utcOffsetDays = 25569;

    // The number of milliseconds in  a day
    /**
     */
    private final static long msInADay = 24 * 60 * 60 * 1000;

    /**
     * This is package protected so that the worksheet might detect
     * whether or not to override it with the column cell format
     */
    static final WritableCellFormat defaultDateFormat =
            new WritableCellFormat(DateFormats.DEFAULT);

    // The number of days between 1 Jan 1900 and 1 March 1900. Excel thinks
    // the day before this was 29th Feb 1900, but it was 28th Feb 19000.
    // I guess the programmers thought nobody would notice that they
    // couldn't be bothered to program this dating anomaly properly
    /**
     */
    private final static int nonLeapDay = 61;

    /**
     * Class definition for a dummy variable
     */
    protected static final class GMTDate {
        public GMTDate() {
        }
    }

    ;

    /**
     * Constructor invoked by the user API
     *
     * @param c the column
     * @param r the row
     * @param d the date
     */
    protected DateRecord(int c, int r, Date d) {
        this(c, r, d, defaultDateFormat, false);
    }

    /**
     * Constructor invoked by the user API
     *
     * @param c the column
     * @param r the row
     * @param d the date
     * @param a adjust timezone
     */
    protected DateRecord(int c, int r, Date d, GMTDate a) {
        this(c, r, d, defaultDateFormat, false);
    }

    /**
     * Constructor invoked from the user API
     *
     * @param c the column
     * @param r the row
     * @param st the format for the date
     * @param d the date
     */
    protected DateRecord(int c, int r, Date d, CellFormat st) {
        super(Type.NUMBER, c, r, st);
        date = d;
        calculateValue(true);
    }

    /**
     * Constructor invoked from the user API
     *
     * @param c the column
     * @param r the row
     * @param st the format for the date
     * @param d the date
     * @param a adjust for the timezone
     */
    protected DateRecord(int c, int r, Date d, CellFormat st, GMTDate a) {
        super(Type.NUMBER, c, r, st);
        date = d;
        calculateValue(false);
    }

    /**
     * Constructor invoked from the API
     *
     * @param c the column
     * @param r the row
     * @param st the date format
     * @param tim time indicator
     * @param d the date
     */
    protected DateRecord(int c, int r, Date d, CellFormat st, boolean tim) {
        super(Type.NUMBER, c, r, st);
        date = d;
        time = tim;
        calculateValue(false);
    }

    /**
     * Constructor invoked when copying a readable spreadsheet
     *
     * @param dc the date to copy
     */
    protected DateRecord(DateCell dc) {
        super(Type.NUMBER, dc);
        date = dc.getDate();
        time = dc.isTime();
        calculateValue(false);
    }

    /**
     * Copy constructor
     *
     * @param c the column
     * @param r the row
     * @param dr the record to copy
     */
    protected DateRecord(int c, int r, DateRecord dr) {
        super(Type.NUMBER, c, r, dr);
        value = dr.value;
        time = dr.time;
        date = dr.date;
    }

    /**
     * Calculates the 1900 based numerical value based upon the utc value held
     * in the date object
     *
     * @param adjust TRUE if we want to incorporate timezone information
     * into the raw UTC date eg. when copying from a spreadsheet
     */
    private void calculateValue(boolean adjust) {
        // Offsets for current time zone
        long zoneOffset = 0;
        long dstOffset = 0;

        // Get the timezone and dst offsets if we want to take these into
        // account
        if (adjust) {
            // Get the current calender, replete with timezone information
            Calendar cal = Calendar.getInstance();
            cal.setTime(date);

            zoneOffset = cal.get(Calendar.ZONE_OFFSET);
            dstOffset = cal.get(Calendar.DST_OFFSET);
        }

        long utcValue = date.getTime() + zoneOffset + dstOffset;

        // Convert this to the number of days, plus fractions of a day since
        // 01 Jan 1970
        double utcDays = (double) utcValue / (double) msInADay;

        // Add in the offset to get the number of days since 01 Jan 1900
        value = utcDays + utcOffsetDays;

        // Work round a bug in excel.  Excel seems to think there is a date
        // called the 29th Feb, 1900 - but this was not a leap year.
        // Therefore for values less than 61, we must subtract 1.  Only do
        // this for full dates, not times
        if (!time && value < nonLeapDay) {
            value -= 1;
        }

        // If this refers to a time, then get rid of the integer part
        if (time) {
            value = value - (int) value;
        }
    }

    /**
     * Returns the content type of this cell
     *
     * @return the content type for this cell
     */
    public CellType getType() {
        return CellType.DATE;
    }

    /**
     * Gets the binary data for writing
     *
     * @return the binary data
     */
    public byte[] getData() {
        byte[] celldata = super.getData();
        byte[] data = new byte[celldata.length + 8];
        System.arraycopy(celldata, 0, data, 0, celldata.length);
        DoubleHelper.getIEEEBytes(value, data, celldata.length);

        return data;
    }

    /**
     * Quick and dirty function to return the contents of this cell as a string.
     * For more complex manipulation of the contents, it is necessary to cast
     * this interface to correct subinterface
     *
     * @return the contents of this cell as a string
     */
    public String getContents() {
        return date.toString();
    }

    /**
     * Sets the date in this cell
     *
     * @param d the date
     */
    protected void setDate(Date d) {
        date = d;
        calculateValue(true);
    }

    /**
     * Sets the date in this cell, taking the timezone into account
     *
     * @param d the date
     * @param a adjust for timezone
     */
    protected void setDate(Date d, GMTDate a) {
        date = d;
        calculateValue(false);
    }


    /**
     * Gets the date contained in this cell
     *
     * @return the cell contents
     */
    public Date getDate() {
        return date;
    }

    /**
     * Indicates whether the date value contained in this cell refers to a date,
     * or merely a time.  When writing a cell, all dates are fully defined,
     * even if they refer to a time
     *
     * @return FALSE if this is full date, TRUE if a time
     */
    public boolean isTime() {
        return time;
    }

    /**
     * Gets the DateFormat used to format the cell.  This will normally be
     * the format specified in the excel spreadsheet, but in the event of any
     * difficulty parsing this, it will revert to the default date/time format.
     *
     * @return the DateFormat object used to format the date in the original
     *     excel cell
     */
    public DateFormat getDateFormat() {
        return null;
    }
}



